The goal is to develop knowledge of the relationship of benign rectosigmoid polyps and cancer of the colon (including the rectum). Specific aims are evaluation of the colon cancer mortality rate in persons who have had one or more surgically-confirmed polyps and comparison of colo-rectal cancer incidence and death rates according to histologic features of the previously removed polyps. A retrospective follow-up study is proposed. A population-based group of 2,500 men and women with surgically-confirmed large bowel polyps (primarily rectosigmoid) will be identified by use of pathology records in Rhode Island hospitals state-wide. Subjects will have had their index admission in the period 1959-70, and will have been 35-79 years old at that time. The cohort will be followed up by use of medical records, death certificates, city directories, and other existing resources. Slides of the benign tissue will be retrieved for all the cases of colon cancer that are identified, and for a sample of non-cases. The slides will be reviewed according to a standard protocol in order to assess the features of the polyps, especially to distinguish neoplastic from hyperplastic polyps, and to assess the villous component (if any) and the extent and severity of dysplasia. The death rate from colon cancer in the cohort will be compared to the rate experienced by Rhode Island residents with the same age and sex distribution. By use of the case-control within a cohort approach, the incidence and mortality rates from colon cancer will be correlated with histologic features of the benign tissue removed. Death rates from other causes also will be evaluated, and rates of recurrence of large bowel polyps will be estimated. The findings will bear on the natural history of colon polyps, and on the clinical prognosis of people with this condition. The results may be useful in planning follow-up protocols for patients with colon polyps and screening programs for colon cancer.